Determination of sub‐ppb epichlorohydrin levels in water by on‐line solid‐phase extraction liquid chromatography/tandem mass spectrometry

A new sensitive and selective method based on on‐line solid‐phase extraction (SPE) coupled to liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI‐MS/MS) using a triple quadrupole mass spectrometer has been developed for the determination of epichlorohydrin (ECH) in different types of water samples. ECH is not easily determined directly by ESI‐MS as it is not readily ionized, and it has a low molecular mass and high polarity. Thus, prior derivatization of ECH was necessary, employing 3,5‐difluorobenzylamine as a derivatizing agent with Fe(III) as a catalyst. In order to achieve accurate quantification, correcting for matrix effects, losses in the derivatization process and instrumental deviations, isotope labelled ECH (ECH‐d₅) was added as an internal standard (IS) to the water samples. The method was validated based on European SANCO guidelines using drinking and other types of treated water spiked at two concentration levels (0.1 and 1.0 µg/L), the lower level having been established as the limit of quantification (LOQ) of the method. Satisfactory accuracy (recoveries between 70 and 103%), precision (RSD <20%) and linearity (from 0.05 to 50 µg/L, r >0.99) were obtained. The limit of detection (LOD) was set up at 0.03 µg/L. The method was applied to different water samples (drinking water and water samples collected from a municipal treatment water plant). In order to enhance confidence, five selected reaction monitoring (SRM) transitions were acquired, thus obtaining a simultaneous reliable quantification and identification of ECH in water, even at sub‐ppb levels. Copyright © 2009 John Wiley & Sons, Ltd.